717
FXUS61 KBOX 170211
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
910 PM EST THU JAN 16 2025
SYNOPSIS
A WEAK LOW PRESSURE SYSTEM WILL BRING A PERIOD OF LIGHT SNOW SHOWERS
TONIGHT, MAINLY FOR AREAS NEAR THE SOUTH COAST, CAPE AND
ISLANDS. TEMPERATURES THEN MODERATE FRIDAY, AND ESPECIALLY BY
SATURDAY, AHEAD OF AN APPROACHING COLD FRONT. THIS COLD FRONT
WILL BRING A PERIOD OF MAINLY RAIN SHOWERS LATER SATURDAY INTO
SATURDAY EVENING. DRY WEATHER SHOULD PREVAIL FOR THE FIRST PART
OF SUNDAY. HOWEVER, A LOW PRESSURE PASSING BY OFFSHORE WILL
LIKELY BRING A PERIOD OF SNOW OR RAIN CHANGING TO ALL SNOW LATE
SUNDAY INTO EARLY MONDAY. THIS WILL BE FOLLOWED BY AN ARCTIC
OUTBREAK LATER MONDAY INTO WEDNESDAY WITH BELOW ZERO WIND
CHILLS.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
KEY MESSAGES:
* LIGHT SNOW SHOWERS TONIGHT MAINLY FOR THE CAPE/ISLANDS
* AN INCH OR SO OF SNOW ACCUMULATION POSSIBLE FOR MVY/ACK
* OVERNIGHT LOWS MAINLY IN THE UPPER TEENS TO THE LOWER 20S
SHORTWAVE COUPLED WITH WEST TO SOUTHWEST FLOW/OCEAN ENHANCEMENT WILL
RESULT IN LIGHT SNOW SHOWERS FOR THE FIRST HALF OF THE
NIGHT...MAINLY TOWARDS THE CAPE AND ISLANDS BUT MAY BRIEFLY OCCUR
FURTHER INLAND. FORCING IS RATHER LIMITED...SO NOT REALLY EXPECTING
MUCH MORE THAN A COATING TO HALF INCH OF SNOW...EXCEPT FOR MARTHAS
VINEYARD/NANTUCKET WHERE AN INCH OR SO OF SNOW ACCUMULATION WILL BE
POSSIBLE. THIS ACTIVITY SHOULD EXIT THE REGION NOT TOO LONG AFTER
MIDNIGHT. OTHERWISE...WE SHOULD GRADUALLY SEE PARTIAL CLEARING
TOWARD DAYBREAK FROM WEST TO EAST. OVERNIGHT LOW TEMPS WILL MAINLY
BE IN THE UPPER TEENS TO THE LOWER 20S.
SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/
KEY MESSAGES:
* TRENDING ABOVE NORMAL AND DRIER
WEAK HIGH PRESSURE TAKES OVER DURING THIS PORTION OF THE
FORECAST. WINDS GRADUALLY TURN SW AS THIS HIGH PRESSURE MOVES
OFFSHORE, AND INCREASES AS A COLD FRONT APPROACHES FROM THE
WEST. SHOULD BE PLENTY OF SUNSHINE FOR MOST, BUT THE CAPE AND
ISLANDS MAY STILL HAVE SOME LINGERING CLOUDS THROUGH FRIDAY
MORNING. THE MAINLY CLEAR SKIES ARE EXPECTED TO BE SHORT-LIVED,
WITH INCREASING CLOUDS FRIDAY NIGHT AHEAD OF A WARM FRONT.
LONG TERM /SATURDAY THROUGH THURSDAY/
KEY MESSAGES...
* MUCH WARMER AND BREEZY ON SAT WITH TEMPS IN THE MID TO UPPER 40S.
* ROUND OF RAIN SHOWERS LATE SAT INTO SAT EVENING.
* PERIOD OF SNOW OR RAIN CHANGING TO SNOW LATE SUN INTO EARLY MON.
* ARCTIC OUTBREAK LATER MON INTO WED WITH BELOW ZERO WIND CHILLS.
DETAILS...
SATURDAY...
MID LEVEL RIDGING EXITS EAST ON SATURDAY WHILE A TROUGH OF LOW
PRESSURE AND ASSOCIATED COLD FRONT APPROACHES FROM THE WEST. THIS
BEGINS TO COMPRESS THE PRESSURE GRADIENT AND WINDS WILL PICK UP ON
SATURDAY, GUSTING 20-25 MPH. THESE WILL BE RELATIVELY MILD SOUTHERLY
WINDS THOUGH, AHEAD OF A COLD FRONT, SO IT WILL BE QUITE MILD DURING
THE DAY, IN THE UPPER 40S. THUS, THE BULK OF THE PRECIPITATION
RESULTING FROM A SHORTWAVE TROUGH AND SURFACE LOW PASSING OVERHEAD
WILL FALL AS WIDESPREAD LIGHT TO MODERATE RAIN. THE ONLY EXCEPTION
MAY BE IN THE HIGHEST TERRAIN OF THE BERKSHIRES, BUT APPRECIABLE
ACCUMULATION ISN'T EXPECTED.
SUNDAY AND MONDAY...
THE FOCUS THEN SHIFTS TO ANOTHER, MORE ROBUST SYSTEM EXPECTED TO
IMPACT THE REGION LATE SUNDAY INTO EARLY MONDAY. BEFORE IT ARRIVES,
RESIDUAL PREFRONTAL MILD AIR IS STUBBORN TO MOVE OUT SO TEMPS WILL
LIKELY ONCE AGAIN BE ON THE MILD SIDE, WARMEST OVER SOUTHEAST MA
WHERE LOW 40S ARE POSSIBLE. 12Z GUIDANCE CAME IN A BIT MORE
AGGRESSIVE WITH THE TRAILING WAVE EXITING THE SOUTHEAST AND
INTENSIFYING A SURFACE LOW UP THE EASTERN SEABOARD OVERNIGHT. AT
THIS DISTANCE IN TIME, THERE REMAINS LOW CONFIDENCE ON AMOUNTS GIVEN
A WIDE RANGE OF TRACKS/STRENGTHS IN THE GLOBAL GUIDANCE. THE
FORECAST GENERALLY TAKES THE MIDDLE ROAD BETWEEN THE MORE AMPLIFIED
UKMET/CMC AND THE LESS AMPLIFIED ECMWF. AT PRESENT THE NATIONAL
BLEND OF MODELS INDICATES GENERALLY A 30-50% CHANCE OF AT LEAST 3
INCHES OF SNOW.
MONDAY NIGHT THROUGH MID WEEK...
A BLAST OF ARCTIC AIR IS SET TO ARRIVE FOR EARLY TO MID WEEK WITH
THE COLDEST AIRMASS YET SEEN THIS SEASON IN SOUTHERN NEW ENGLAND.
THANKS TO A DEEP TROUGH DIGGING INTO THE CENTRAL AND EASTERN U.S.
WE'LL SEE 850 MB TEMPS DROP AS LOW AS -25C CENTERED AROUND TUESDAY
NIGHT. ON EITHER SIDE (FROM TUESDAY MORNING THROUGH THURSDAY MORNING)
LOW TEMPERATURES IN THE SINGLE DIGITS (NEAR 0 IN THE HIGHEST
ELEVATIONS) ARE LIKELY. WIND CHILL VALUES MAY EVEN REACH SUB -10C.
"MILD" AIR, OR AT LEAST MILDER AIR, RETURNS BY THURSDAY.
AVIATION /01Z FRIDAY THROUGH TUESDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT...MEDIUM CONFIDENCE (SNOW CHANCES)
LIGHT SNOW SHOWERS DEVELOP THIS EVENING, MAINLY AFTER 00Z WITH
THE HIGHER PROBABILITIES TOWARDS THE SOUTH COAST, CAPE, AND
ESPECIALLY ACK. THIS WILL BRING MVFR CEILINGS TO THE SOUTH
COAST/CAPE AND ISLANDS. CAN'T RULE OUT BRIEF LOCALIZED IFR
CONDITIONS WITH THE GREATEST RISK AT ACK, WHERE UP TO 2 INCHES
OF SNOW ACCUMULATION WILL BE POSSIBLE. THERE IS A CHANCE FOR
SCATTERED LIGHT SNOW SHOWERS/FLURRIES FOR THE OTHER TERMINALS
WITH BRIEF MVFR POSSIBLE IN ANY OF THE HEAVIER SNOW SHOWERS.
SHOWERS DIMINISH BEFORE MIDNIGHT FOR MOST AREAS WITH THE
EXCEPTION OF CAPE/ISLANDS. LIGHT SW WINDS BECOMING NW.
FRIDAY...HIGH CONFIDENCE.
VFR. NW WINDS 5-10 KNOTS, BECOMING SW FRIDAY AFTERNOON.
KBOS TAF...MEDIUM CONFIDENCE IN TAF.
THERE REMAINS A LOW RISK FOR LIGHT SNOW SHOWERS WITH SOME
ACCUMULATION, BUT FLURRIES ARE MORE LIKELY. THE PRIMARY WINDOW
WOULD BE BETWEEN 01-05Z.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK /SATURDAY THROUGH TUESDAY/...
SATURDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY. CHANCE
RA.
SATURDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.
CHANCE RA, SLIGHT CHANCE SN.
SUNDAY: VFR. CHANCE SN, SLIGHT CHANCE RA.
SUNDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.
CHANCE SN.
MARTIN LUTHER KING JR DAY: VFR. BREEZY. SLIGHT CHANCE SN.
MONDAY NIGHT THROUGH TUESDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH- GREATER THAN 60 PERCENT.
HIGH CONFIDENCE.
GENERALLY LIGHT WINDS (15 KT AND LESS) AND SEAS ARE EXPECTED
THROUGH FRIDAY NIGHT.
OUTLOOK /SATURDAY THROUGH TUESDAY/...
SATURDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. SEAS UP TO 5 FT. RAIN LIKELY.
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. RAIN
LIKELY.
SUNDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF RAIN.
SUNDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.
CHANCE OF SNOW, RAIN LIKELY. AREAS OF VISIBILITY 1 TO 3 NM.
MARTIN LUTHER KING JR DAY: WINDS LESS THAN 25 KT. ROUGH SEAS UP
TO 9 FT. CHANCE OF SNOW, CHANCE OF FREEZING SPRAY.
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF ROUGH SEAS. CHANCE OF FREEZING
SPRAY, SLIGHT CHANCE OF SNOW.
TUESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...BELK/BW
NEAR TERM...FRANK
SHORT TERM...BELK
LONG TERM...BW
AVIATION...BELK/BW
MARINE...BELK/BW
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